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The preparation of the bulky secondary amide N-(2,6-diisopropylphenyl)-2,2-dimethylpropanamide and the determination of its crystal structure at 173(2) K are reported. The structure displays disorder of the [.sup.t]Bu methyl groups due to thermal motion and an infinite N-H x x x x O=C hydrogen-bonded chain described by a [C.sup.1.sub.1](4) graph set. Reaction of this amide with Zn[Cl.sub.2] or Zn[Br.sub.2] in tetrahydrofuran (THF) results in dihalo-(tetrahydrofurano)-(N-(2,6-diisopropylphenyl)-2,2-dimethylpropanamido)-zinc(II) complexes (Cl, Br) for which the crystal structures have also been determined. These complexes, as well as a chloroform solvate of the dichloro-complex, contain N-H x x x x X-Zn hydrogen-bonded chains described by [C.sup.1.sub.1](6) graph sets. Evaporative crystallization results in the loss of both chloroform and THF to afford crystals determined to be bis([[mu].sub.2]-chloro)-dichloro-bis(N-(2,6-diisopropylphenyl)-2,2-dimethylpropanamido)-dizinc(II) by single crystal X-ray diffraction. This dimeric complex shows a complex network of N-H ... Cl-Zn hydrogen bonds describable by [C.sup.1.sub.1](6), [C.sup.1.sub.1](8), and [C.sup.2.sub.2](16) chains, small [R.sup.4.sub.4](28) molecular 'squares', and larger [R.sup.6.sub.6](44) rings. Key words: synthesis, X-ray crystallography, hydrogen-bonding, graph sets, amide ligands. La preparation de l'amide secondaire volumineuxN-(2,6-diisopropylphenyl)-2,2-dimethylpropanamide et la determination de sa structure cristalline a 173(2) K sont rapportees. La structure presente le desordre des groupes methyle du [.sup.t]Bu en raison du mouvement thermique et une chaine infinie de liaisons hydrogene N-H x x x x O=C decrite par un ensemble de graphes [C.sup.1.sub.1](4) La reaction de cet amide avec le Zn[Cl.sub.2] ou le Zn[Br.sub.2] dans le tetrahydrofurane (THF) conduit a des complexes dihalo-(tetrahydrofurano)-(N-(2,6-diisopropylphenyl)-2,2-dimethylpropanamido)zinc(II) (Cl, Br) pour lesquels les structures cristallines ont egalement ete determinees. Ces complexes, ainsi qu'un solvate chloroforme du dichloro-complexe, contiennent des chaines de liaisons hydrogene N-H ... X-Zn decrites par des ensembles de graphes [C.sup.1.sub.1](6). La cristallisation par evaporation entraine la perte de chloroforme et de THF pour donner des cristaux determines comme bis([[mu].sub.2]-chloro)-dichloro-bis(N-(2,6-diisopropylphenyl)-2,2-dimethylpropanamido)dizinc(II) par diffraction des rayons X sur monocristal. Ce complexe dimerique presente un reseau complexe de liaisons hydrogene N-H ... Cl-Zn descriptible par des chaines de type [C.sup.1.sub.1](6), [C.sup.1.sub.1](8) et [C.sup.2.sub.2](16), des petits << carres >> moleculaires de type [R.sup.4.sub.4](28) et de plus grands anneaux de type [R.sup.6.sub.6](44). Mots-cles: synthese, radiocristallographie, liaisons hydrogene, ensembles de graphes, ligands amide., Introduction Amides A (Chart 1) are relatively less common coordination ligands despite their high prevalence as components of natural and synthetic macromolecules (i.e., proteins and polymers). (1,2) Zincis the second-most [...]

The title compound Dipp(H)P-P(H)Dipp where Dipp = 2, 6-diisopropylyphenyl has been prepared starting from DippP[H.sub.2] viaDippPHLi reacting 2:1 with BrC[H.sub.2]C[H.sub.2]Br. A high-resolution single-crystal X-ray diffraction study at 153 ± 2Kprovides an accurate description of the structure in the solid state, only the fourth dihydro diorganophosphane to have been so characterized. The Raman spectrum of the solid shows an intense, broad peak for P-H stretching at 2314 [cm.sup.-1] and two peaks at 460 and 450 [cm.sup.-1] for P-P stretching, assignments confirmed by RHF/6-31G+(3d, 2p) frequency calculations undertaken on the anti conformers. [sup.31]P, [sup.31]P{¹H}, ¹H{[sup.31]P}, and [sup.13]C{¹H} solution NMR spectra in CD[Cl.sub.3] are consistent with the presence of 58% meso and 42% rac diastereomers. Analysis of their AA'XX' spin systems enabled calculation of ¹[J.sub.PP]. values of (-)189 and (-)205 Hz, respectively. A B3LYP/6-31G(d, p) computational analysis of the energetics of rotation about the P-P bond in both diastereomers shows that the anti and two gauche conformers are likely to be populated approximately equally in each. The resulting average φ angles (torsions of the phosphorus lone pairs) are 110° for meso and 103° for rac; the smaller φ angle fits with the larger JPP, value for the rac isomer. Key words: diphosphanes, P-P single bond, conformational analysis, crystallography, Raman spectroscopy, RHF and DFT quantum computation, multinuclear NMR spectroscopy. Le compose indique dans le titre, Dipp(H)P-P(H)Dipp oU Dipp = 2, 6-diisopropylyphenyl, a ete prepare a partir de DippP[H.sub.2] par la reaction de DippPHLi avec BrC[H.sub.2]C[H.sub.2]Br (2:1). Un etude de diffraction des rayons-X a haute resolution a 153 ± 2 K fournit une description precise de la structure a l'etat solide, seul le quatrieme dihydro diorganophosphane avoir ete ainsi caracterise. Le spectre Raman du solide montre un large, intense pic pour etirement P-H a 2 314 [cm.sup.-1] et deux pics a 460 et 450 [cm.sup.-1] pour etirement P-P, attributions confirmees par calculs de frequence RHF/6-31G+(3d, 2p) effectuees sur les conformeres decales. Les spectres RMN [sup.31]P, [sup.31]P{¹H}, [sup.31]P{¹H} et [sup.13]C{¹H} de solution dans CDCI3 sont en accord avec la presence des diastereoisomeres meso (58%) et rac (42%). L'analyse de leurs systemes de spins AA'XX' permet le calcul des JPP= valeurs de (-)189 et (- )205 Hz, respectivement. Une analyse informatique B3LYP/6-31G(d, p) de l'energetique de rotation autour de la liaison P-P dans les deux diastereoisomeres montre que les conformeres anti et gauches sont peuplees approximativement egale. Les angles φ moyennes resultant (torsions des paires non liees phosphore) de 110° pour meso et 103° pour rac; l'angle φ plus petit correspond a la valeur la plus grande ¹[J.sub.PP]' pour l'isomere rac. Mots-cles : diphosphanes, liaison P-P simple, conformerie, cristallographie, calculs quantiques HF et DFT, spectroscopie Raman, spectroscopie RMN multinucleaire., Introduction There is currently intense interest in dehydrocoupling reactions, (1) including reactions leading to the stoichiometric (2-5) and catalytic (6-10) formation of dihydro diphosphanes R(H)P-P(H)R. Coupling reactions of primary phosphanes [...]

The reaction of [[3,5-[Ph.sub.2]-[C.sub.2][N.sub.3]S].sub.2] with [[CpCr[(CO).sub.3]].sub.2] in toluene at room temperature forms an adduct via a Cr-S bond, formulated as CpCr[(CO).sub.3]S[N.sub.3][C.sub.2][Ph.sub.2], which has fitting NMR, IR, and combustion analysis data. The structure was determined by a single-crystal X-ray structure diffraction study ([P2.sub.1]/n, a = 8.4611(17) Å, b = 20.509(4) Å, c = 11.757(2) Å, β = 104.453(7)°). The Cr-S bond length of 2.4908(11) A corresponds to a bond order of 1.0 from > 90 values for CpCr[(CO).sub.x] or [Cp.sup.*]Cr[(CO).sub.x] moieties (x = 2, 3) bonded to S, which are used to establish a Pauling-type bond order scale specific to this class of compounds. Similar reactions of fluorinated thiatriazinyls derived from [[3-Ph-5-C[F.sub.3]-[C.sub.2][N.sub.3]S].sub.2] or [[4-MeO[C.sub.6][H.sub.4]-5-C[F.sub.3]-[C.sub.2][N.sub.3]S].sub.2] are accompanied by the loss of CO to produce CpCr[(CO).sub.2]S[N.sub.3][C.sub.2]PhC[F.sub.3] (P1, a = 8.0929(8) Å, b = 10.3160(10) Å, c = 11.2405(11) Å, α = 70.032(2)°, β = 72.076(2)°, γ = 82.375(2)°) and CpCr[(CO).sub.2]S[N.sub.3](CC[F.sub.3])([C.sub.6][H.sub.4]OC[H.sub.3]) ([P2.sub.1]/c, a = 8.1311(7) Å, b = 24.284(2) A, c = 9.1025(8) Å, β = 97.218(2)°), also fully characterized by spectroscopy and crystallography. Their measured Cr-S bond lengths, 2.2987(14) and 2.2965(11) Å, correspond to bond orders of 1.5. (U/R)B3PW91/6-311+G(2df,2p)//B3PW91/6-31G(2d,p) hybrid density functional theory (DFT) calculations show that the tricarbonyl complex has an unusual σ bond. However, the dicarbonyl complexes of the fluorinated thiatriazinyls are π onded. Key words: multiple bonds, thiazyl radicals, trifluoromethyl, chromium-sulfur bonds, chromium-nitrogen bonds, π bonding, single-crystal X-ray crystallography, density functional theory (DFT) calculations. Resume: La reaction de [[3,5-[Ph.sub.2]-[C.sub.2][N.sub.3]S].sub.2] avec [[CpCr[(CO).sub.3]].sub.2] dans du toluene a la temperature ambiante donne un produit d'addition par l'intermediaire d'une liaison Cr-S, formulee comme CpCr[(CO).sub.3]S[N.sub.3][C.sub.2][Ph.sub.2], pour qui le RMN, IR et des donnees d'analyse de combustion sont juste. La structure a ete determinee par un etude de diffraction monocristalline des rayons-X ([P2.sub.1]/n, a = 8.4611(17) Å, b = 20.509(4) Å, c = 11.757(2) Å, 0 = 104.453(7)°). La longueur du liaison Cr-S, 2.4908(11) Å, correspond a un ordre de liaison de 1,0 a partir de > 90 valeurs pour CpCr[(CO).sub.x] or [Cp.sup.*]Cr[(CO).sub.x] groupements (x = 2, 3) lie a S qui sont utilises pour etablir une echelle de Pauling d'ordre du liaison specifique pour cette classe de composes. Des reactions similaires en utilisant les thiatriazinyls fluores derives de [[3-Ph-5-C[F.sub.3]-[C.sub.2][N.sub.3]S].sub.2] ou [[4-MeOC6H4-5-CF3-[C.sub.2][N.sub.3]S].sub.2] sont accompagnes par la perte de CO pour produire CpCr[(CO).sub.2]S[N.sub.3][C.sub.2]PhC[F.sub.3] (P1, a = 8.0929(8) Å, b = 10.3160(10) Å, c = 11.2405(11) Å, a = 70.032(2)°, β = 72.076(2)°, γ = 82.375(2)°) et CpCr[(CO).sub.2]S[N.sub.3](CC[F.sub.3])([C.sub.6][H.sub.4]OC[H.sub.3]) ([P2.sub.1]/c, a = 8.1311(7) Å, b = 24.284(2) Å, c = 9.1025(8) Å, 0 = 97.218(2)°), egalement entierement caracterise par spectroscopie et de la cristallographie. Leurs longueurs des liaisons Cr-S, 2.2987(14) et 2.2965(11) Å, correspond a un ordre de liaison de 1.5. Calculs a la theorie de la fonctionnelle de la densite (TFD) hybrides (U/R)B3PW91/6-311+G(2df,2p)//B3PW91/6-31G(2d,p) montrer que le complexe de tricarbonyl a une liaison inhabituelle σ, mais les complexes thiatriazinyls fluores sont lies en facon π. Mots-cles: liaisons multiple, radicaux thiazyle, trifluoromethyle, liaisons chrome-soufre, liaisons chrome-azote, liaisons π, diffraction monocristalline des rayons-X, calculs a la theorie de la fonctionnelle de la densite (TFD)., Introduction A major topic in modern main group chemistry is the degree to which elements other than carbon can partake in multiple bonding and unsaturation. (1-17) Thus, all the properties [...]

A series of phenyl-substituted bis(isobenzofuran)s in which the furan moieties are linked by 1,3-phenylene, 1,4-phenylene, or 4,4'-biphenylene linkers have been prepared in only two steps. They are comparable to diphenylisobenzofuran in their absorption and luminescent properties, their electrochemistry, and their reactivity. Their degree of similarity to diphenylisobenzofuran was found to depend significantly on the nature of the linking group. Diels-Alder reaction of the title compounds and subsequent aromatization gave very rapid access to penta- or hexa-aryl products. Key words: isobenzofuran, diphenylisobenzofuran, fluorescence, UV spectroscopy, electrochemistry, pentaphenyl, hexaphenyl. On a prepare, par des reactions n'impliquant que deux etapes, une serie de bis(isobenzofuranes) substitues par un groupe phenyle dans lesquels les portions furanes sont liees 738par des troncons 1,3-phenylene, 1,4-phenylene ou 4,4'-biphenylene. Par leurs proprietes d'absorption et de luminescence, d'electrochimie et de reactivite, ces produits se comparent au diphenylisobenzofurane. On a observe que leur degre de similarite avec le diphenylisobenzofurane depend beaucoup de la nature du groupe qui les relie. La reaction de Diels-Alder des composes mentionnes dans le titre et l'aromatisation subsequente des produits obtenus donne un acces tres rapide aux produits penta- ou hexaryles. Mots-cles : isobenzofurane, diphenylisobenzofurane, fluorescence, spectroscopie UV, electrochimie, pentaphenyle, hexaphenyle. [Traduit par la Redaction], Commercially available 1,3-diphenylisobenzofuran (1, Fig. 1) has found wide application in the identification of reactive olefins, as an analytical tool for measuring the rate of singlet-oxygen generation and is of [...]

The unsaturated redox-active cluster [[[Pd.sub.3][(dppm).sub.3](CO)].sup.n+] (n = 0,1, or 2) reacts with ethylene dicarboxylic esters and a variety of terminal acetylenes (but not PhC ≍ CPh) in all three charge states. In particular, the radical cations [[[[Pd.sub.3][(dppm).sub.3](CO)(RC ≍ CR')]'.sup.??+] can be produced by several routes: one-electron electrochemical reduction of the dication adducts, comproportionation of the neutral and dicationic adducts, as well as the direct complexation of alkyne to the known radical cation [[[Pd.sub.3][(dppm).sub.3](CO)].sup.??+]. Compared with the latter, each of the adducts have significantly extended lifetimes and classify as persistent radicals in solution. The alkyne adducts have been characterized by voltammetry (cyclic and rotating disk electrode), by UV - vis titrations and by MALDI-TOF mass spectra from dithranol matrices. Isotropic solution EPR spectra of the adducts with R = R'= MeOC(O) and EtOC(O), as well as those with R'= H and R = [C.sub.6][H.sub.5], F[C.sub.6][H.sub.4], HC ≍ CC6H4, and EtO have been obtained. Full line shape fitting simulations demonstrate that all display coupling to six different [sup.31]P (I = 1/2) and to one to three [sup.106]Pd (I = 5/2) nuclei. The A([sup.31]P) values range from a low of 3.0 x [10.sup.4] to a high of 180.5 x [10.sup.4] [cm.sup.-1]; this variation is caused by changes in the contribution of P s orbitals to the SOMO resulting from structural distortions of the [Pd.sub.3][P.sub.6] core upon alkyne coordination. Key words: electrochemistry, redox state, electron paramagnetic resonance, catalytic model, palladium, bridging phosphine. Le cluster insature [[[Pd.sub.3][(dppm).sub.3](CO)].sup.n+] (n = 0,1, ou 2) reagit, quelle que soit sa charge, sur des derives acetyleniques de formule generale RCCR' comme des di-esters acetyleniques et sur une variete de derives acetyleniques vrais R'CCH mais pas sur PhC ≍ CPh pour conduire aux adduits [[[Pd.sub.3][(dppm).sub.3](CO)(RCCR')].sup.n+] (n = 0,1,2). En particulier les radicaux cations [[[Pd.sub.3][(dppm).sub.3](CO)(RC ≍ CR')].sup.??+] peuvent etre generes par plusieurs voies : soit par reduction mono-electronique de l'adduit dicationique correspondant [[[Pd.sub.3][(dppm).sub.3](CO)(RC ≍ CR'].sup.2+] soit par une reaction d' antidismutation entre l'adduit neutre et l'adduit dicationique et enfin par la complexation directe de l'alcyne sur l'espece monocationique paramagnetique electrogenere [[[Pd.sub.3][(dppm).sub.3](CO)].sup.??+]. Compare a ce dernier, chacun des adduits paramagnetiques obtenus sont beaucoup plus stables et peuvent donc etre plus facilement caracterises en solution. Les differentes methodes mises en oeuvre pour la caracterisation des adduits reposent sur la voltammetrie cyclique et sur electrode tournante, la spectroscopie UV - visible, la spectrometrie de masse (MALDI-TOF) et par analyse RPE, methode pour laquelle des spectres des adduits [[[Pd.sub.3][(dppm).sub.3](CO)(RC ≍ CR')].sup.??+] avec R = R'= MeOC(O) and EtOC(O) d'une part et avec R'= H, R = [C.sub.6][H.sub.5], F[C.sub.6][H.sub.4], HC ≍ C[C.sub.6][H.sub.4] et EtO d'autre part, ont ete obtenus avec une bonne resolution. La simulation des spectres a permis de tirer toutes les constantes de couplage aux six atomes de phosphore [sup.31]P (I = 1/2) et avec un, deux ou trois des atomes de palladium 106Pd (I = 5/2). Pour expliquer la variation importante des differentes valeurs des constantes A([sup.31]P) qui correspond a 3.0 x [10.sup.4] pour la valeur la plus faible a 180.5 x [10.sup.4] [cm.sup.-1] pour celle la plus elevee, un changement de la contribution de l'orbitale s du phosphore a l'orbitale SOMO, est retenue qui resulte d'une distorsion structurale du coeur [Pd.sub.3][P.sub.6] par coordination de l'alcyne. Mots-cles : electrochimie, etat redox, resonance paramagnetique electronique, modele catalytique, palladium, cluster, diphosphine., Introduction Puddephatt and co-workers (1-3) first reported a convenient synthetic route to trifluoracetate and hexafluorophosphate salts of the cyclic tripalladium cluster [[[Pd.sub.3][(dppm).sub.3]([μ.sub.3]-CO)].sup.2+] in which each diphenylphosphinomethane (dppm) ligand bridges two [...]

Abstract: The 2:1 adduct of benzyne with 2-methylanisole is shown to have the bisbenzotricyclic structure 6,6a,11,11a-tetrahydro-5-methoxy-6-methyl-5,6,11-metheno-5H-benzo[a]fluorene by a single-crystal X-ray diffraction study ([C.sub.20][H.sub.18]O: [Pca2.sub.1], a = 15.0497(17), b = 9.87783(11), [...]

The first magnesium and zinc boraamidinate (bam) complexes are synthesized via metathetical reactions between dilithio atoms and Grignard reagents or MCl2 (M=Mg, Zn). The results show that the bam anionic radical [PhB(N(super t)Bu)(sub 2)](super .-) can be stabilized by coordination to a variety of early main-group metal centers to provide neutral radicals whose relative stabilities are compared and discussed.

The reaction of Cl3PNSiMe3 with primary lithium amides is a simple synthetic route to a variety of amino/iminophosphoranes of the type (RNH)3PNSiMe3 (R=alkyl). Further reaction of such species with (super n)BuLi under mild conditions produce the unsymmetrical tetraimidophosphates {Li3[P(NR)(sub 3-)(NSiMe3)]}.

The bulky primary phosphane 2,6-diisopropylphenylphosphane, DipP[H.sub.2], has been prepared from 1-bromo-2,6-diisopropylbenzene via the reaction of the Grignard reagent with P[Cl.sub.3]. The resulting mixed phosphonous dihalides DipP[(Cl,Br).sub.2] are reduced with LiAl[H.sub.4] to yield the title compound in reasonable yield and on a synthetically useful scale. DipP[H.sub.2] is also used to prepare the monosilylated derivatives DipPHSi[(C[H.sub.3]).sub.3] and DipPH{Si[(C[H.sub.3]).sub.2]-t-Bu} as well as the disilylated compounds DipP[{Si[(C[H.sub.3]).sub.3]}.sub.2] and DipP[{Si[(C[H.sub.3]).sub.2]-t-Bu}.sub.2]. All products have been fully characterized by IR, mass, and NMR spectroscopy. The crystal structure of DipPH{Si[(C[H.sub.3]).sub.2]-t-Bu} was determined from single-crystal diffraction data: [C.sub.18][H.sub.33]PSi, P[2.sub.1]/c, Z = 4, a = 8.5768(10), b = 28.104(3), c = 8.1102(4) [Angstrom], [beta] = 93.341(3)[degrees] (R = 0.0518). Changes in the NMR spectrum of DipPH{Si[(C[H.sub.3]).sub.2]-t-Bu} were observed over the temperature range 178-380 K. Barrier heights were determined from the peak separation at low temperature and the coalescence points: [DELTA]G[double dagger] [approximately equal to] 40 kJ [mol.sup.-1] for C(aryl)--P bond rotation and [approximately equal to] 72 kJ [mol.sup.-1] for pyramidal inversion at phosphorus. Key words: crystal structure, 2,6-diisopropylphenyl, bulky substituents, steric congestion, dynamic NMR, primary phosphane, silyl phosphane.

The reaction of N,N'-bis(2,6-diisopropylphenyl)carbodiimide with lithium 2,6-diisopropylanilide, quenching with water and recrystallization from heptane produces the symmetric guanidine [[DipNH].sub.2]C=NDip which crystallizes in the triclinic system, space group P[bar]1, a = 10.6513(11), b = 10.8997(11), c = 16.2961(17) [Angstrom], [alpha] = 80.524(12), [beta] = 78.921(13), [gamma] = 70.060(12)[degrees], V = 1735.2(3) [[Angstrom].sup.3], Z = 2. The molecule crystallizes with three perpendicular 2,6-diisopropylphenyl groups, which surround and shield the central C[N.sub.3] unit, and provide (almost) three-fold symmetry around the central atom. Its dynamic solution behaviour has been studied by VT NMR between -90 and +180[degrees]C, and is consistent with three distinct barriers to N-[C.sub.Ar] rotation. Preliminary estimates of the Gibbs free energy of activation for the lower two barriers are 56 [+ or -] 2 and 73 [+ or -] 2 kJ [mol.sup.-1]. Reaction of the title compound with Mo[(CO).sub.6] in refluxing n-heptane produces [[DipNH].sub.2]C= NDip*Mo[(CO).sub.3], a complex in which Mo[(CO).sub.3] is [[eta].sup.6]-coordinated to one of the diisopropylpbenyl rings. Key words: crystal structure, diisopropylaniline, guanidine, bulky ligands.

N,N'-bis-(2,6-diisopropylphenyl)trifluoroacetamidine has been prepared for the first time from 2,6-diisopropylaniline and the trifluoroacylation reagent TFAP via the imidoylchloride. The crystal structure of the amidine was determined, indicating that it crystallizes in the Z-anti tautomer, in contrast to the nonfluorinated analogue, which is E-anti in the solid state. In solution, as indicated by NMR spectroscopy, it exists in two isomeric forms. The amidine reacts with Mo[(CO).sub.6] to produce a coordination complex with Mo[(CO).sub.3] in which the ligand is also in the Z-anti geometry, the metal is [[eta].sup.6]-coordinated to the imino-2,6-diisopropylphenyl ring, and the amino N-H unit is directed towards the metal, as determined by a single-crystal X-ray structure. Unlike the analogous nonfluorinated acetamidine, there is no indication of an intermediate in which the neutral amidine is coordinated in a monodentate fashion to an Mo[(CO).sub.5] unit, which we now attribute to the predominant geometry of the ligand, both in the solid state and in solution, being Z-anti. The high steric bulk of this superamidine ligand apparently prevents the formation of a metal-metal bonded [Mo.sub.2][(amidinate).sub.4] as observed previously in a redox reaction between N,N'diphenylbenzamidine and Mo[(CO).sub.6] under similar thermal reaction conditions. Key words: trifluoromethyl, superamidine, amidine, molybdenum, carbonyl, coordination.

Deep blue (E=S) or green (E=Se) solutions are produced by the air oxidation of the cluster compounds (Li(sub2)E(NtBu)(sub3)(sub2)) in toluene. The ESR spectra comprises a septet of decuplets and simulations show that secondary hyperfine splitting occurs from interaction of the unpaired electron with equivalent Li ions. Such spectra are assigned to the radion anions SeO(NtBu)(sub2) and SeO(sub2)(NtBu).

The compounds XC6H4CN5S3, XC6H4CN3S2Cl2, (XC6H4CN3S2)2 and XC6H4CN3S2.C7H10, where X = 4-CH3, 4-Cl, 3-CF3, 4-CF3, 4-CH3O and 4-C6H5, were synthesized. Single-crystal x-ray diffraction determined the structure of (4-ClC6H4CN3S2)2 to be in the triclinic space group P1 with a = 6.107(1) Angstrom (A), b = 12.070(2) A, c = 13.206 A, alpha = 113.73(1) degrees, beta = 99.04(2) degrees, gamma = 97.53(2) degrees and Z = 2. This compound crystallizes as a head-to-head dimer. Dimers are packed head-to-tail, with a pattern of two dithiatriazine rings above two phenyl rings in columns along the bc diagonal.

A silylated derivative of naphtha[1,2-c:5,6-c]difuran, 1,3,6,8-tetrakis(tert-butyldimethylsilyl) naphtha[1,2-c:5,6-c]difuran, is isolated and its X-ray crystal structure is determined. Crystal structures of two cyclophanes derived from the reaction of naphtha[1,2-c:5:6-c]difuran and bis(imide) or bis(ester) dienophiles have shown differences in the conformation of the aliphatic chain seen in the solid state.

The density functional calculations for the group 15 radicals [[PhB[([mu]-[N.sup.t]Bu).sub.2].sub.2][M.sub..] (M = P, As, Sb, Bi) which predict a pnictogen-centered SOMO with smaller contributions to the unpaired spin density arising from the nitrogen and boron atoms are discussed. The results from the analysis of the chemical redox behavior of the [[PhB[([mu]-[N.sup.t]Bu).sub.2].sub.2]As anion and cation showed that a two-electron process is favor over a one-electron process.

The reaction between [[CpCr[(CO).sub.3]].sub.2] and dithiadiazolyl dimers [[[S.sub.2][N.sub.2]CNR.sub.2]] (R = substituted aryl ring) leads to the isolation of a series of the first [pi] organometallic complexes of C,N,S-heterocyclic compounds.

Detailed electrochemical and spectroelectrochemical studies of the oxidation of complexes reveal the presence of an exceptionally stable dinuclear Pt cation 2(super +) that have led to the informed chemical synthesis and structural characterization of a rare form of, halide-free Pt(II)-Pt(III) cation. Results reveal that the unpaired electron in the 2(super +) cation is distributed equally between the two Pt nuclei and imply that oxidation of 2 to 2(super +) leads to the formation of metal-to-metal hemibond.

The neutral compound ((super t)BuNH)3PNSiMe3 is mono-, di-, or trilithiated by reactions with a stoichiometric amount of (super n)BuLi results in the formation of imido analogues of [H2PO4](super -), [HPO4](super 2-), and [PO4](super 3-), respectively. The X-ray structure and EPR spectra of THF solutions of the stable neutral radical {[Me3SiN)P(u3-N(super t)Bu3)][mu3-Li(THF)]3 (O-(super t)Bu)} are discussed.

The synthesis, NMR spectroscopy, single-crystal X-ray structure, and solution electrochemistry of the new compound [2,6-{CH(CH[sub 3])}2C[sub 6]H[sub 3]][sub 3] As, abbreviated as Dipp[sub 3]As, is reported. The molecule, prepared by reaction of AsCl[sub 3] with a preformed aryl copper reagent, Dipp[sub 4]Cu[sub 4], crystallizes in the hexagonal space group R3 as a racemic twin. The sum of angles around As, ΢ {CAsC}, is 329.13(3)&#° in the X-ray structure and 329.17° from an R-B3LYP/6-31G(d,p) hybrid density functional theory calculation. The aromatic rings are quite distorted with both the ipso carbon and especially the As atom significantly out of plane by 0.503(3)A. The ambient temperature NMR spectrum fits for C[sub 3] symmetry implying that inversion is slow on the NMR timescale. Cyclic voltammetry on a glassy carbon electrode in CH[sub 2]Cl[sub 2] with 0.4 M [[sup n]Bu[sub 4]N][PF[sub 6]] over scan rates of 0.05-0.8 V s[sup -1] and temperatures of 22 ± 2°C produced one quasi-reversible process with E[sub m1] = +0.43 V at a scan rate of 0.20 Vs[sup -1] and a second irreversible process with a peak potential of+ 1.45 V (v. Fc[sub +/0]). The diffusion coefficient has been measured as 3.3 + 0.1 x 10[sub -6] cm s[sup -1] in CH[sub 2]Cl[sub 2] solution containing 0.4 M [nBu4N][PF[sub 6]]. Chemical oxidation with AgPF[sub 6] in CH[sub 2]Cl[sub 2] in degassed solutions in sealed vessels allowed for recording of characteristic EPR spectra; at 293 K, a ([sup 75]As) = 26.1 mT and g = 2.021. In frozen solution, an almost isotropic spectrum is obtained (g|| = 2.000 mT and g± = 2.003 mT) and the hyperfine splitting constants are a || = 47.9 and a = 19.0 mT, leading to an estimate for the structure being slightly pyramidal with ΢ {CAsC} = 351°. [ABSTRACT FROM AUTHOR]

A general synthetic route to 3-trifluoromethyl-5-aryl-1λ3-1,2,4,6-thiatriazinyl radicals was developed. X-ray structures were obtained for all five neutral radicals and show that they exist in the solid state as cofacial dimers linked by S···S contacts. X-ray structures were also obtained for two of the precursor chlorothiatriazines along with several aryl N-imidoylamidines, p-methoxybenzamidine, and N-chlorosulfonyl-N,N′-benzamidine. Cyclic voltammetric studies were performed on the [R2C2N3S]• radicals in CH3CN and CH2Cl2 with [nBu4N][PF6] as the supporting electrolyte under vacuum conditions in an all-glass electrochemical cell. The results provide quasi-reversible formal potentials for the [R2C2N3S]−/0 process in the range of −0.61 to −0.47 V, irreversible peak potentials for the [R2C2N3S]0/+ process from 0.59 to 0.91 V at lower concentrations, and the appearance of a second, reversible oxidation process from 0.69 to 0.94 V at higher concentrations (versus the Fc0/+ couple; Fc = ferrocene). This behavior was indicative of monomer-dimer equilibrium in solution, as ascertained from digital models of the voltammograms. There is a small but measurable trend in both the oxidation and reduction potentials with varying remote aryl substituents. EPR spectra were obtained for all five neutral radicals in CH2Cl2 solutions, which confirm the concentration of the unpaired electron density on the heterocyclic core. Trends were also seen in the hyperfine splitting constants aN with varying remote aryl substituents. Calculations were performed for all three oxidation states of the [R2C2N3S]−/•/+ monomeric rings; the resulting theoretical redox energies correlate well with solution phase voltammetric data. [ABSTRACT FROM AUTHOR]